Search-as-you-type inside arrays - elasticsearch

Question

I am trying to implement a search-as-you-type query inside an array.
This is the structure of the documents:
{
"guid": "6f954d53-df57-47e3-ae9e-cb445bd566d3",
"labels":
[
{
"name": "London",
"lang": "en"
},
{
"name": "Llundain",
"lang": "cy"
},
{
"name": "Lunnainn",
"lang": "gd"
}
]
}
and up to now this is what I came with:
{
"query": {
"multi_match": {
"fields": ["labels.name"],
"query": name,
"type": "phrase_prefix"
}
}
which works exactly as requested.
The problem is that I would like to search also by language.
What I tried is:
{
"query": {
"bool": {
"must": [
{
"multi_match": {
"fields": ["labels.name"],
"query": "london",
"type": "phrase_prefix"
}
},
{
"term": {
"labels.lang": "gd"
}
}
]
}
}
}
but these queries act on separate values of the array.
So, for example, I would like to search only Welsh language (cy). That means that my query that contains the city name should match only values that have "cy" on the "lang" tag.
How do I write this kind of query?

Answer 1

Internally, ElasticSearch flattens nested JSON objects, so it can't correlate the lang and name of a specific element in the labels array. If you want this kind of correlation, you'll need to index your documents differently.
The usual way to do this is to use the nested data type with a matching nested query.
The query would end up looking something like this:
{
"query": {
"nested": {
"path": "labels",
"query": {
"bool": {
"must": [
{
"multi_match": {
"fields": ["labels.name"],
"query": "london",
"type": "phrase_prefix"
}
},
{
"term": {
"labels.lang": "gd"
}
}
]
}
}
}
}
}
But note that you'll need to also specify nested mappings for your labels, e.g.:
"properties": {
"labels": {
"type": "nested",
"properties": {
"name": {
"type": "text"
/* you might want to add other mapping-related configuration here */
},
"lang": {
"type": "keyword"
}
}
}
}
Other ways to do this include:
Indexing each label as a separate document, repeating the guid field
Using parent/child documents

Answer 2

You should use Nested datatype in mapping instead of Object datatype. For detail explanation refer this:
https://www.elastic.co/guide/en/elasticsearch/reference/current/nested.html
So, you should define mapping of your field something like this:
{
"properties": {
"labels": {
"type": "nested",
"properties": {
"name": {
"type": "text"
},
"lang": {
"type": "keyword"
}
}
}
}
}
After this you could query using Nested Query as:
{
"query": {
"nested": {
"path": "labels",
"query": {
"bool": {
"must": [
{
"multi_match": {
"fields": ["labels.name"],
"query": "london",
"type": "phrase_prefix"
}
},
{
"term": {
"labels.lang": "gd"
}
}
]
}
}
}
}
}